|Budget Amount *help
¥2,500,000 (Direct Cost : ¥2,500,000)
Fiscal Year 1997 : ¥800,000 (Direct Cost : ¥800,000)
Fiscal Year 1996 : ¥1,700,000 (Direct Cost : ¥1,700,000)
A key to successful living cationic polymerization is the judicious choice of a counterion for a particular growing end. Namely, a suitably nucleophilic counterion stabilize the growing end to lead to living cationic polymerization. To generalize the principle for living cationic polymerization, we examined the feasibility of living cationic polymerization in polar solvents where the dissociated free ionic species may be involved.
Living Polymerization of Isobutyl Vinyl Ether(IBVE). At-78ﾟC,living polymerization was induced with the HCI-IBVE adduct(1)/ZnCl_2 system in CH_2Cl_2 and a EtNo_2/CH_2Cl_2 mixture, whereas similar systems with EtAlCl_2 led to conventional cationic polymerization. In these polar media, both systems gave polymers with very similar and low isotacticity (meso<approximately equal>56%), indicating that the propagating reaction is mediated by free ions. Thus, regardless of solvent polarity, or involvement of free ions or ion pairs, living cationic polymerization requi
res a suitably nucleophilic counteranion.
Living polymerization of p-t-Butoxystirene (tBOS). To demonstrate the feasibility of living polymerization by free ions other cationically polymerizable monomers, cationic polymerization of tBOS,which has higher reactivity among stirene derivatives, was examined with the 1/ZnCl_2 initiating system at-15ﾟC in polar solvents. Although tBOS was polymerized at a relatively higher temperature, living polymerization also occurred in the presence of the free ionic species as observed with IBVE.
In summary, living cationic polymerization can be achieved in a strongly polar medium, where the dissociated free ionic species is involved in the propagating reaction. This is the first example of living cationic polymerization whose propagating reaction is mediated by free ions. In addition, now that the novel reaction conditions have been developed in this study, new types of living polymers would be obtained from a variety of monomers whose living polymerization have not been operable under the reaction conditions reported before.